1. Field of the Invention
The present invention relates to systems for maintaining multiple temperature regions, and in particular, to a device and associated method for the automated, bulk thermal cycling of fluids, solutions, and/or reactants.
2. Description of the Related Art
The polymerase chain reaction (PCR) is widely used by research professionals around the world as a means to amplify small strands of DNA. Typically, PCR is performed using automated thermal cyclers that alternately heat and cool numerous small tubes containing the PCR reaction mixture. Such a process uses a static reactor having discrete, confined spaces in which the reaction occurs when exposed to different temperatures in a repetitive sequence. This process is time intensive, labor intensive, and inefficient, as the tubes must be individually filled with the reactants, closed, processed through the automatic cycler, opened, and finally drained of the reaction product that contains the desired amplified DNA.
Accordingly, continuous thermal cyclers were developed to eliminate the need for using a multitude of small tubes to amplify DNA via PCR by using a dynamic reactor. Rather than using small tubes, continuous thermal cyclers use a constant or continuous stream of fluid repetitively passed through different temperature zones to amplify DNA. One example of a continuous thermal cycler is disclosed in U.S. Pat. No. 5,270,183 issued on Dec. 14, 1993, to Corbett et al. Corbett et al. disclose a device and method for DNA amplification in which a PCR reaction mixture is injected into a carrier fluid with which the PCR reaction mixture is immiscible, and the carrier fluid then passes through a plurality of temperature zones to facilitate DNA amplification within the PCR reaction mixture. The function of this device is to accelerate the processing of a multitude of different DNA strands contained in discrete pockets or plugs, hence the need for a carrier fluid that is immiscible with the PCR reaction mixture that acts to separate the different DNA strands. This device is not designed to produce mass quantities of DNA.
Moreover, the Corbett et al. device is not designed to be easily and quickly adaptable to different PCR reaction requirements. For example, the preferred arrangement for passing the carrier fluid through the temperature zones is to wrap tubing conveying the carrier fluid around separate cylinders maintained at different temperatures. Modifying the device for different reaction conditions therefore requires re-wrapping the tubing around one or more of the cylinders a different number of times, unwrapping the tubing around one or more of the cylinders to replace one or more of the cylinders with different cylinders, re-routing the tubing around the cylinders in different orders, or another such labor-intensive procedure. Additionally, efficiency and fine temperature control is reduced as the reaction mixture pockets pass from one cylinder to the next and thermal energy is unintentionally lost or gained at such “gaps.”
Another example of a continuous thermal cycler is disclosed in Curcio, M. and Roeraade, J. (2003, published on web 2002) Continuous Segmented Flow Polymerase Chain Reaction for High-Throughput Miniaturized DNA Amplification, Anal. Chem. 75, 1-7. This device similarly is designed for numerous small sample mixtures separated by an immiscible fluid. Rather than using separate cylinders as different temperature zones as in the Corbett et al. device, however, this device uses separate thermally controlled water baths as temperature zones. This device is not designed for easy modification for providing a number of different reaction conditions, as additional water baths would have to be prepared and added for such modification. Use of this device also entails adding, checking, and draining water from the baths on a periodic basis, as well as cleaning of the water bath containers.
For the foregoing reasons, there is a need for a continuous thermal cycler that is designed to mass produce DNA strands, that is easily adaptable to different PCR reaction requirements, and that is efficient in operation.